This invention relates to a combustion chamber of an internal-combustion engine, especially to a combustion chamber of an internal-combustion engine in which the piston crown has a special block-wall.
A two-stroke engine must use a fuel injection system in order to get complete combustion of fuel and to reduce exhaust emission. The usual fuel injection two-stroke engine is shown in FIG. 1A. The fuel injection system 5 is installed just above the cylinder cover 21 of cylinder head 2. In the compression stroke, piston 1a moves up from the bottom dead center. Fuel is injected during this period. Another example is shown in FIG. 1B with the injection nozzle 5 set on the cylinder wall 3. This type is much simpler and cheaper than that shown in FIG. 1A due to the low pressure injection. However, the usual designs have the following disadvantages:
1) In FIG. 1A, the injection nozzle 5 is installed in the cylinder head 2. The injection nozzle 5 must resist high temperature and high pressure of combustion gas it therefore uses higher injection pressure to inject fuel. Consequently, the cost of this kind of injection system is high.
2) In FIG. 1B, the injection system is installed on the cylinder wall. The time from normal injection to ignition is not long enough to obtain fuel vaporization and a good fuel mixture. Some of the fuel will be pushed into the exhaust port 32 by fresh air which comes from scavenging ports 31, because the top of piston head lacks a special block-wall design. This is called a short circuit of fuel, which causes fuel waste and exhaust emission.
3) In FIG. 1B, when the fuel is injected from nozzle 5, fuel droplets will attach on the surfaces of the combustion chamber causing wall wetting resulting in high emissions caused by unburned hydrocarbon.